This application is related to co-pending applications Balachandran 13-18-18-40-1 and Balachandran 11-16-38, which are hereby incorporated by reference.
The invention relates to relates generally to wireless communication networks and, more particularly, to a method and system for efficiently providing voice communications over wireless and/or cellular networks while using full rate channels.
The widespread growing popularity of the Internet has encouraged wireless communication system developers to continually improve the data communication capabilities of their systems. In response to this need, various standards bodies have formulated and continue to formulate new third generation (3G) standards which support higher data rates. For example, standards organizations such as the European Telecommunications Standards Institute (ETSI), the Association of Radio Industries and Broadcasting (ARIB) and the Telecommunications Industry Association (TIA) are continually developing standards to support faster and more efficient wireless communications.
Similarly, the wireless communications industry is often developing and implementing new wireless transmission protocols which provide faster, more robust and more efficient data communications over air interfaces. For example, GSM continues to evolve. In another example, general packet radio service (GPRS) has been developed as a packet-switched upgrade for the well known time division multiple access (TDMA) system. In a further advancement in the art, enhanced GPRS (EGPRS) has also been developed.
Presently, GSM, GPRS and EGPRS physical layers have the following characteristics: a carrier that consists of two 200 kHz bandwidth segments of the allocated GSM spectrum, 45 MHz apart, one for the downlink and one for the uplink; time is divided into frames with a multiframe comprising 52 frames and spans 240 msec.; each frame consists of 8 time slots; one slot on one carrier is referred to as a GSM channel; there is a one-to-one correspondence between a slot (numbered j, j=0, . . . 7) on a downlink carrier at frequency (f) and an uplink slot (numbered j) on the corresponding uplink carrier (f+45 MHz); a transmission in a slot is referred to as a burst; and a block consists of a predefined set of four bursts on the same slot.
Radio access bearers are currently being designed in order to provide real time services in EGPRS Phase II. However, recent approaches rely on using the existing burst based random access channels on the uplink and block based assignment channels on the downlink. Each block is interleaved and transmitted over 4 bursts (20 msec). However, investigation has shown systems based on 20 msec granularity require at least a 60 msec delay budget. Also, the investigation has shown transmission of assignments to multiple mobile stations within a single 20 msec message often is inefficient due to low packing and is incompatible with interference reduction techniques such as smart antennas and power control. As a result, block based assignment channels according to the recent approaches can result in excessive control overhead and excessive delays for statistical multiplexing of real time transfers (e.g. voice talkspurts). It is desirable to provide a better access and assignment system and method.
In order to efficiently use the high capacity of a wireless or a cellular data telecommunication system (e.g., GPRS or EGPRS), it is also desirable to provide voice and data multiplexing capability as well as statistical multiplexing of voice users. Currently these cellular data telecommunication systems are designed to provide primarily non-real time (delay insensitive) data services. Conversational speech and other real time interactive communications are delay sensitive and require the design of new control mechanisms to provide fast control channels to meet the critical delay requirements. Therefore, there is a need to redesign wireless data telecommunication systems to provide such control capabilities to make them suitable for multiplexing both non-real-time services and real-time services, such as conversational speech.
Presently under GSM, a mobile user assigned to some channels has to receive on even bursts in one multi-frame and odd-bursts in the next multiframe. Such switching between even and odd bursts is not well suited for dynamic assignment of uplink and downlink channels. Therefore, there is a need to redesign wireless data telecommunication systems to provide different burst-channel structures that are suited to dynamic assignment of uplink and downlink channels. A redesign for half rate channels and especially for full rate channels. Present full rate channel structure can be very wasteful of available bandwidth and delay times by using the present channel structures and present interleaving.
This need is met by the method of the present invention wherein systems and methods are described that enable efficient and flexible multiplexing of both real-time and non-real-time services over full rate channels of wireless data telecommunication systems.
Briefly stated in accordance with one aspect of the invention, the aforementioned problems are addressed and an advance in the art achieved by providing a system for communicating using wireless time division multiplexed communications in which time is divided into a plurality of frames and each frame is divided into N data bursts. This system includes a first multiplexer defining a half rate channel as a series of bursts that occur periodically every N bursts once per frame, a second multiplexer for defining a full rate channel as two consecutive half rate channels; and a transmitter transmitting the full rate channel from a first station to a second station.
In accordance with a specific aspect of the invention, the aforementioned problems are addressed by providing a system for communicating using wireless time division multiplexed communications in which time is divided into a plurality of frames and each frame is divided into N data bursts. This system includes a first multiplexer defining a half rate channel as a series of bursts that occur periodically every N bursts once per frame, a second multiplexer for defining a full rate channel as two consecutive half rate channels; and a transmitter transmitting the full rate channel from a first station to a second station. The system also includes an interleaver which interleaves bursts using 0246/1357 interleaving.
In accordance with another specific aspect of the invention, the aforementioned problems are addressed by providing a method for communicating using wireless time division multiplexed communications in which time is divided into a plurality of frames and each frame is divided into N data bursts. This method includes the steps of interleaving bursts using a 0246/1357 sequence to provide a plurality of half rate channels, using two consecutive half rate channels of the plurality of half rate channels to provide a full rate channel, and transmitting the full rate channel made up of the interleaved bursts from a first station to a second station.